The present invention relates to apparatus for severing elongated rod-shaped commodities, such as cigarette rods, filter rods or the like. More particularly, the invention relates to improvements in apparatus for reciprocating a device which is used in a rod severing apparatus (such severing apparatus are known as cutoffs) to guide, confine and support the rod during cutting by the knife or knives of the cutoff.
Cutoffs are used in cigarette rod making, filter rod making and like machines to sever a continuous rod at regular intervals so that the rod, which moves lengthwise, yields a succession of discrete rod-shaped articles constituting plain cigarettes, cigars or cigarillos or filter rod sections of unit length or multiple unit length. A cutoff of such character is disclosed, for example, in commonly owned U.S. Pat. No. 3,518,911 granted July 7, 1970 to Helmut Niemann et al. A guide is provided to confine the rod in the region of the knife and such guide serves to support the rod as well as to constitute a counterknife for the orbiting knife or knives of the cutoff. The guide must move back and forth, and is caused to advance forwardly in the direction of movement and at the speed of the rod while a knife performs its cutting stroke. The same holds true when the cutoff is used to sever a continuous filter rod or a continuous hollow cylindrical rod which is to yield a succession of tubes of the type often used in the making of certain types of filter mouthpieces. For the sake of simplicity, the following description will deal with the cutoffs and guides for cigarette rods but it will be readily understood that the invention can be embodied with equal advantage in cutoffs for rods which are to be subdivided into cigars, cigarillos or cheroots as well as in cutoffs which are used in filter rod making machines.
The cutoff is a highly important and very sensitive component of a cigarette rod making machine. Its knife or knives must sever the rod in a plane extending exactly at right angles to the axis of the rod, each cut must be clean and the rod must be properly confined, supported and guided in the region of the severing station. Since a modern cigarette maker turns out in excess of 100 cigarettes per second, the guide must be caused to oscillate at a frequency of several thousand times per minute and in such a way that it invariably moves forwardly with and at the speed of the rod when a knife moves across the path of and thereby severs the rod. The speed of the rod is in the range of several hundred meters per minute. This means that the guide must be accelerated from a starting position to the exact speed of the rod, it must move at the speed of the rod during severing of the rod, it must be decelerated to zero speed, and it must move at a high speed and counter to the direction of movement of the rod back to its starting position several thousand times per minute. The guide has a narrow transversely extending slot through which the cutting edge of a knife moves in the course of the severing operation which, as explained above, takes place while the guide and the rod move in the same direction and at the same speed. The consistency of the rod is such that it cannot offer a satisfactory resistance to deformation in the course of a severing operation, i.e., the knife which approaches and penetrates into the rod at a frequency of several thousand times per minute would flex the rod in the absence of suitable means for holding the rod portion at the severing station against deformation, i.e., against flexing of the rod laterally of and away from the prescribed path wherein the rod advances axially under the action of the customary garniture in the cigarette rod making machine.
Heretofore known apparatus which are used to move the rod guide in the region of the cutoff back and forth at a frequency of several thousand times per minute exhibit a number of serious drawbacks. First of all, the mass of such apparatus is substantial with attendant application of enormous stresses to the bearings for as well as to the material of the guide and other elements which share or initiate the movements of the guide. Secondly, oscillatory movements of the guide at the aforementioned high frequency are accompanied by the generation of readily detectable noise which is bothersome to attendants. Still further, the inertia of moving parts is sufficiently high to prevent an increase of the oscillation frequency to a value which is required in a modern high-speed cigarette maker so that the maker must be operated at less than maximum capacity only because the guide for the rod in the cutoff of the cigarette maker cannot move back and forth at the rate at which the orbiting knife or knives of the cutoff are capable of severing the rod. In other words, the output of the entire machine is limited because the oscillation frequency of the rod guide cannot be increased to a value which is commensurate with maximum capacity of the cutoff and/or other component parts of the cigarette maker.